Method of forming a prosthetic dental appliance and an impression tray therefor



Aug. 19, 1969 N. A. HANA 3. 5

METHOD OF FORMING A PROSTHETIC DENTAL APPLIANCE AND AN IMPRESSION TRAY THEREFOR Filed April 20. 1967 FIGJ FIG. 2

INVENTOR NORMAN A. HANA BUCKHORN, BLORE KLARQUIST6 SPARKMAN ATTORNEYS United States Patent 3,461,560 METHOD OF FORMING A PROSTHETIC DEN- TAL APPLIANCE AND AN IMPRESSION TRAY THEREFOR Norman A. Hana, Vancouver, Wash, assignor to Deklin Dental Laboratory Company, Portland, Oreg., a corporation of Oregon Filed Apr. 20, 1967, Ser. No. 632,269 Int. Cl. A61c 9/00, 13/08 US. CI. 32-17 12 Claims ABSTRACT OF THE DISCLOSURE A plastic tray is formed from a plaster model of a patients mouth, such tray being individually adapted for taking a further impression of the patients mouth. This tray has a tissue bearing area, e.g. corresponding to the patients palate, and is relieved elsewhere for receiving impression-taking material. The tray is also provided with a plurality of apertures corresponding to the abutment teeth to which a partial appliance is to be attached. The impression tray is placed in the mouth with the abutment teeth extending therethrough, and with crowns seated upon such abutment teeth, after which a compound lock is made between such tray and the crowns to form a rigid pattern from which an accurate model of mouth can be made for the construction of the appliance.

Background of the invention In the course of fitting a patient with a partial denture, a number of abutment teeth are usually cut down for the reception of crowns and a first impression is taken of the mouth in a relatively soft material. A plaster model may then be formed from this impression and crowns are constructed to conform with the plaster model. Since the first impression is usually taken with a relatively soft material, the first model is frequently not an accurate representation of the mouth.

It is desirable that a second impression be taken with the crowns in place and a further model be constructed so that the proper interrelation between crowns, the appliance, and the rest of the mouth can be established. In accordance with one prior art method, the prepared crowns were seated in the patients mouth and a second impression in plaster was taken over the crowns and the various tissue areas of the mouth. During this procedure, it was possible and likely that the crowns would move from their desired position. Furthermore, after the plaster hardened, such impression usually had to be fractured to remove it from the mouth. The information from the second impression was then not likely to be much more accurate than the first impression.

Summary of the invention In accordance with the present invention, a first impression is taken of the patients mouth and a first model is formed therefrom. From this model, crowns are prepared and also a custom made tray is prepared having a tissue bearing area matching a first area of the patients "ice month, the tray being relieved elsewhere for receiving impression material. This tray also includes a plurality of apertures corresponding in position to abutment teeth. Using this tray a second impression is taken of the patients mouth with the prepared crowns seated in place by the dentist, these crowns extending through the aforementioned apertures.

The tray including such tissue bearing area and the crowns are properly and accurately seated and adjusted by the dentist, and thereafter a lock is established between the crowns and tray by means of a hardening material applied over the apertures. The tray is then removed from the mouth. The tray now accurately defines the interrelation between properly seated crowns, the aforementioned tissue-bearing area, and the impression 0t other portions of the mouth which maybe of interest. The three elements are securely interrelated and can be used to form a second model which will accurately represent this interrelation. The second mode-l is employed in the construction of the dental appliance.

It is accordingly an object of the present invention to provide an improved method of forming a partial denture which will accurately fit the mouth of the patient.

It is another object of the present invention to provide an improved method of forming a dental appliance, which method is of improved accuracy and less likely to cause error in the construction of the appliance.

It is a further object of the present invention to provide an improved method for forming partial dentures, which method provides an improved adaptation between tissue areas of a patients mouth and the crowns forming the attachment to the denture.

It is a further object of the present invention to provide an improved method of taking a dental impression for the preparation of a partial denture which allows for adjustment and correct seating of crowns in their relation to the denture.

It is a further object of the present invention to provide an improved dental impression tray which is adaptable for establishing a desired relation between the elements of a partial denture.

It is a further object of the present invention to provide an improved dental tray allowing the adjustment of crowns relative to an impression.

It is another object of the present invention to provide an improved dental tray including a tissue bearing area for adaptation with respect to a patients mouth.

Drawings FIG. 1 is an exploded drawing showing the interrelation between an improved dental tray according to the present invention and a patients mouth including abutment teeth prepared for the placement of a dental appliance.

FIG. 2 is a view of the FIG. 1 tray in place with crowns extending through apertures in such tray.

FIG. 3 is a cross section of such tray in place, illustrating a method step according to the present invention wherein dental crowns are located with respect to the tray.

Detailed description According to the method of the present invention, a prosthetic dental appliance is formed in the following manner. The description will pertain to a partial upper denture by way of example, but it is understood the present invention is not restricted thereto.

First, the dentist prepares abutment teeth for the reception of crowns to which the partial appliance may be attached. This usually involves reducing the abutment teeth in size so the crowns may subsequently be cemented thereto, these crowns providing anchoring means for the partial appliance.

After the preparation of the abutment teeth, a first impression of the mouth is taken in conventional impression tray and employing, for example, hydrocolloid impression material. The impression is taken not only of the abutment teeth, but of the surrounding mouth area ineluding the tissue area such as the mouth roof or palate against which the partial plate of the appliance will bear, and gum ridges which may or may not include further teeth.

The impression thus taken is removed from the mouth, and a plaster or stone model of the mouth is formed therefrom. This model includes the aforementioned abutment teeth as well as tissue area. Unfortunately, this model may not be extremely accurate because the impression material from which it is taken is not absolutely rigid, but in the method of the present invention serves as a stepping stone to the making of an accurate model. Crowns or copings are prepared using the first model.

According to the present invention, a custom made tray is also prepared from the first stone model of the mouth hereinbefore mentioned and which is used to take a second impression in the mouth. The tray is formed of a relatively low temperature fusing thermoplastic material. Before formation of such tray, the model of the mouth may be surveyed, i.e., grooved around the edge of desired tissue contact area of the partial plate. The areas of the model except for the area to be contacted by the partial plate are provided with a coating of wax. The tray is now formed, i.e. molded or cast, around the model so that it will have a matching tissue bearing area, e.g. matching the desired palate areas of the patients mouth which will be contacted by the partial appliance, while being relieved elsewhere by the wax coating. The tray is also provided with apertures in the region of the abutment teeth so that such abutment teeth extend therethrough.

Referring now to FIG. 1, a custom made tray of the type referred to above is indicated at 10. The tray has a tissue bearing palate portion 12 and a trough-shaped portion 14 for extending over the gum ridge. However, trough portion 14 is relieved so that the tray 10 will not touch the mouth of the patient except principally in the area of portion 12. Apertures 16 are provided through which the abutment teeth may extend. These teeth, here three in number, are illustrated at 18, the patients palate being indicated at 20. The tray is provided with an inwardly directed peripheral ridge 17 around each aperture which will desirably press against the gingiva or gum portion around the neck of each abutment tooth. Crowns 22 are designed to be cemented upon abutment teeth 18 and these crowns will also extend through apertures 16. The apertures 16 are sufiiciently large to give ample clearance for crowns 22. The tray preferably is formed with a front handle 15.

Before taking a second impression, the tray is placed in the patients mouth to see if the tissue bearing area 12 comfortably matches the palate of the patient. Desirable changes in the contour of the tissue bearing portion 12 may be accomplished by the dentist at this time. The tray 10, in position, is illustrated in FIG. 2. After the tissue seated later as subsequently described. As seen, the tray the satisfaction of the dentist, the crowns 22 (or copings) may be seated on the abutment teeth 18 but also may be seated later as subsequently described. As seen, the tray 10 does not interfere with the proper positioning of these crowns. An impression material is then placed over the interior surface of the tray 10. Conventional elastic impression material may be employed. The tray is then placed in the mouth so as to take the impression. Referring to FIG. 3, this impression material is indicated at 24 between the relieved portions of tray 10 and the gum ridge 20 of the patient. Ridges 17 tend to keep the impression material from the area of abutment teeth. Any impression material passing ridges 17 is carefully removed from the crowns and the area surrounding the abutment teeth if the crowns have previously been placed. If the crowns have not previously been placed, such area and abutment teeth are cleared of impression material and the crowns are seated. In either case, any impression material extending into this area may be torn away along ridges 17. It is observed that the crowns 22 are in the exact position desired by the dentist, and any remaining errors in the contours of the tissue bearing portion 12 of the tray are corrected by impression material. In taking this impression slight pressure should be applied to the tray so as to make certain the tissue bearing area is firmly seated to give the adaptation desired for seating of the finished appliance. At this time ridges 17 depress the gingiva away from the crowns to help insure correct seating of the crowns. Next, a lock is made between the crowns and the tray to firmly establish the relation between the tray, tissue bearing area 12 and the crowns. This is accomplished by placing a low fusing temperature compound lock material, plaster, or stone which is non-elastic upon hardening or setting around the crowns and upon the tray as indicated at 26, FIG. 3. Hardening of such material firmly locks the crowns to the tray.

Now the tray, the impression material 24, and the crowns 22 are removed as a unit from the patients mouth. The tray may now be employed to cast a second plaster or stone model of the mouth after tooth dies conforming to the abutment teeth are first placed in the crowns. Such second model is a substantially exact duplicate of the mouth, particularly with regard to the position of the abutment teeth with respect to one another and with respect to the tissue area of the palate.

The second model is suitably employed for the manufacture of the partial dental appliance. For example, a wax pattern of the partial is formed, and an investment casting is made thereof in a conventional manner. The crowns, after removal from the tray 10, are then fitted to the partial while mounted on the second model. The finished appliance, since it is made from an exact duplicate of the mouth and has the desired interrelation of crowns and tissue bearing area, will fit the mouth substantially exactly as desired. Other conventional procedures such as enameling, etc. are performed as necessary.

Various changes can be made in the above procedure without departing from the invention. For example, a gold or chrome casting of the patients palate may be formed from the first mentioned model and substituted directly for tissue bearing portion 12 in the tray 10. This casting is physically joined as a part of the tray 10 as by forming the tray around such casting. This casting, which will also subsequently form a part of the dental appliance, is used during the second impression procedure outlined above. As above, the tissue bearing area, here constituting the casting, will have the correct interrelation to crowns 22.

It may also be desirable to employ bite blocks mounted on a tray 10 when the second impression is taken. A bite registration can thus be taken without removing the tray.

Also, according to the method of the present invention, if one or more crowns do not fit properly during the second impression as outlined above, copper band impressions or the like may be taken of the abutment teeth from which new crowns may be made. In such case, the bands are locked to the tray with the locking compound or the like at the same locations as the missing crowns. Thus, desired impressions corresponding to the abutment teeth may be fastened to the tray, whether such impressions are in the form of crowns, copings, or band impressions of the abutment teeth.

The method and tray according to the present invention are thus employed to aid the dentist in checking and rechecking each step in 'his technique in fitting a partial denture or the like. The present method allows the dentist to see and check each step in the most complicated type of impression technique and enables him to provide an appliance that will accurately conform to the patients mouth.

While I have shown and described preferred embodiments of my invention, it will be apparent to those skilled in the art that many changes and modifications may be made without departing from my invention in its broader aspects.

I claim:

1. The method of forming a prosthetic dental appliance comprising the steps or:

preparing a tray including the pattern of a selected tissue area of the month which said appliance is designed to contact,

forming apertures in said tray corresponding to the position of abutment teeth prepared for supporting said appliance,

placing the said tray in the patients mouth with said pattern pressed against said tissue area,

and fastening impressions of said abutment teeth to said tray.

2. A method according to claim 1 wherein said tray including said pattern is formed of plastic.

3. A method according to claim 1 wherein said tray is formed of plastic, but wherein said pattern is formed of metal adapted to provide a part of said appliance.

4. A method according to claim 1 wherein said tray is formed with apertures having inwardly extending peripheral ridges, and wherein said ridges are pressed toward the patients gum surrounding abutment teeth.

5. A method according to claim 1 wherein impressions of said abutment teeth are fastened to said tray by applying over said impressions of said abutment teeth and adjacent areas of said tray a material capable of hardening to a rigid condition,

and after such material hardens, removing said tray whereby an accurate relationship between said tissue area and said impressions of said abutment teeth is established in said tray.

6. A method according to claim 5 wherein said impressions of said abutment teeth comprise crowns placed on said abutment teeth prior to placing or the said hardening material whereby said crowns will. be locked to said tray.

7. A method according to claim 5 wherein dies of said abutment teeth are set in the impressions thereof and a casting is made from said tray to provide a model of the patients mouth portion.

8. The method of forming a prosthetic dental appliance comprising the steps of:

forming with impression material a first impression of a portion of a patients month including prepared abutment teeth and tissue area to which said appliance is to be fitted,

casting a first rigid model from first impression,

preparing a tray from said first rigid model including the pattern of a selected tissue arc-a corresponding to said model, while substantially relieving said tray in selected other areas,

lforrning apertures in said tray corresponding to the position of said abutment teeth,

placing the said tray in the patients mouth with said pattern pressed against said tissue area, and with impression material located in said tray in selected relieved areas to take a second impression,

fastening impressions of said abutment teeth to said tray by applying over said impressions of said abutment teeth and adjacent areas of said tray a material capable of hardening to a rigid condition,

and after such material hardens, removing said tray whereby an accurate relationship between said tissue area and said impressions of said abutment teeth is established in said tray.

9. A method according to claim 8 further including forming a second rigid model in accordance with the impression in said tray,

and forming said prosthetic appliance to fit said second rigid model.

10. A method according to claim 8 wherein the said said impressions of said abutment teeth comprise crowns adapted for seating upon said abutment teeth and secured to said tray within said apertures.

11. A method according to claim 81 wherein said impressions out abutment teeth are hand impressions of abutrnent teeth secured to said tray within said apertures.

12. A method according to claim 8 wherein said apertures are formed with inwardly extending peripheral ridges.

References Cited UNITED STATES PATENTS 2,579,965 12/1951 Robinson 32--17 2,685,134 8/1954 Thompson 32-17 ROBERT PESHOCK, Primary Examiner UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 461, 560 Dated August 19. 1969 Inventofls) NORMAN A. HANA It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 4, Delete "Deklin" and insert instead -Dahlin- Column 3, line 72, Delete in its entirety "seated later as subsequently described. As seen, the tray" and substitute instead --bearing portion 12 is matched to the patient's palate,

Column 6, line 13, after "from" insert --said- SILIJ iii) SEALED FEB171970 Amt:

Edward MFlewher, Ir. WILLIAM E. SGHUYLER, IR;

A w Off Commissioner of Patents t 8 mg 1361' 

